TWI550070B - Switch element comprising a liquid-crystalline medium - Google Patents

Description

Conversion element including liquid crystal medium

The present invention relates to a conversion element that is thermally reactive and that converts between a lower transmission state for radiant energy and a higher transmission state for radiant energy, and which comprises a liquid crystal medium. The invention further relates to the use of a conversion element for regulating the flow of radiant energy between the interior space and the environment and for regulating the temperature of the interior space. The invention further relates to a liquid-crystalline medium characterized in that it comprises a compound of the formula (I), which is used in particular in the above-mentioned conversion element.

The conversion element is used in accordance with the invention for similar openings in windows or in buildings, such as glass doors, skylights and/or glass roofs, for adjusting the amount of light inflow.

For the purposes of the present invention, the term liquid crystal medium is used to mean a material or compound that exhibits liquid crystal properties under specific conditions. The liquid crystal medium preferably exhibits a thermal behavior, and the liquid crystal medium preferably exhibits a temperature-induced phase transition from an isotropic to a liquid crystal phase, preferably to a nematic phase.

For the purposes of the present invention, the term interior space is intended to refer to the interior space of a private, public or commercial building (e.g., a building for office purposes), as well as the interior space of a vehicle. In addition, the term internal space is also intended to be used in the interior space of a building (eg, a greenhouse) that is meant to be purely commercial.

For the purposes of the present invention, the term window is intended to mean any desired light-transmissive opening in a building, transport container or vehicle that is sealed by a solid material.

For the purposes of the present invention, radiant energy flow is used to mean the flow of electromagnetic radiation that is emitted by the sun, passes through the atmosphere and reaches the earth, and the glass sheet absorbs only a small extent or not at all. Electromagnetic radiation may also be emitted by a source other than the sun. Since relatively short-wavelength radiation (UV-B light) and long-wavelength infrared radiation are absorbed by the atmosphere or glass plates, for the purposes of the present invention, the term "radiation energy" is understood to include UV-A light, visible light (VIS). Light) and near-infrared (NIR) light.

Unless specifically defined otherwise, the term light is also intended to mean electromagnetic radiation in the UV-A region, the VIS region, and the near-infrared region.

According to the definitions commonly used in the field of physical optics, UV-A light is understood to mean electromagnetic radiation having a wavelength of from 320 nm to 380 nm for the purposes of the present invention. VIS light should be understood as electromagnetic radiation from 380 nm to 780 nm. Near-infrared light (NIR) is understood to be electromagnetic radiation at wavelengths from 780 nm to 3000 nm. Thus, for the purposes of the present invention, the terms "radiation energy" and "light" are understood to mean electromagnetic radiation having a wavelength of from 320 nm to 3000 nm.

For the purposes of the present invention, the term conversion element thus denotes a device capable of switching between a state having a lower transmission of radiant energy and a state having a higher transmission to radiant energy, the term radiant energy being as defined above. The conversion element can be selectively converted in one or more sub-regions of the radiant energy spectrum. The terms "device" and "conversion element" are used interchangeably hereinafter.

The conversion element of the invention is thermally reactive. However, it may additionally be controlled by one or more other mechanisms, such as electrical or mechanical mechanisms. These other mechanisms preferably do not exist.

Modern buildings are known for their high proportion of glass surfaces, which are aesthetically pleasing and the need for brightness and comfort in the interior. In recent years, it has become equally important for buildings for residential or commercial purposes and/or for public use to be energy efficient. This means that in the cold season of the temperate climate zone (the climate zone in most highly developed industrial countries), as little energy as possible is used for heating purposes and there is no or only a small amount of air conditioning in the interior space during the warm season.

However, a high proportion of the glass surface hinders the achievement of these goals. In the warm temperate climate zone and in the warm season of the temperate climate zone, the glass surface causes the interior space to be heated when exposed to solar radiation. This is because the glass can be penetrated by the radiation in the VIS and NIR regions of the electromagnetic spectrum. The objects in the interior space absorb the permeable radiation and thereby warm it, which leads to an increase in the internal space temperature (greenhouse effect).

This increase in temperature in the interior space behind the glass surface (referred to as the greenhouse effect) is also caused by radiation from internal objects that have absorbed radiation. However, the radiation emitted by such objects is primarily in the infrared spectrum of light (typically at a wavelength of approximately 10,000 nm). It can therefore no longer pass through the glass and "trap" in the space behind the glass.

However, the above-mentioned effects of the glass surface in buildings are not always undesirable: when the external temperature is low, especially in the cold zone or in the cold season of the temperate climate zone, it may be advantageous for solar radiation to heat the interior space due to the greenhouse effect. This reduces the energy required for heating and thus saves costs.

As the energy efficiency of buildings increases, so does the need for devices that control the flow of energy through windows or glass surfaces. In particular, there is a need for a device that is capable of matching the energy flow through the glass surface to the conditions prevailing at a particular time (hot, cold, high solar radiation, low solar radiation).

Particular attention is paid to the supply of such devices in the temperate climate zone, where seasonal variations occur between a combination of warm external temperature combined with high solar radiation and a cold external temperature combined with low solar radiation.

The prior art discloses non-convertible devices that limit energy flow but cannot be modified in a variable manner, and convertible devices that are capable of matching energy flow with individual prevailing conditions. In a convertible device, a device that does not automatically adapt to environmental conditions and a device that automatically adapts to environmental conditions should be distinguished. The latter device is also known as a smart window.

Multi-inlaid glass window units (insulated glass units (IGU)) have long been known for improving the thermal insulation of windows. The continuous two or more glass panes that enclose one or more environmentally isolated gas-filled gaps enable a significant reduction in heat transfer through the window compared to a single glass pane. The prior art additionally discloses coating a glass surface with a thin layer (e.g., a metal layer or a metal oxide layer) (US 3,990,784 and US 6,218,018).

However, it is also impossible to adapt to weather or seasonal conditions if the radiant energy flow is controlled only by coating and/or by the use of insulating glass. For example, attention will be paid to windows that completely transmit sunlight to reduce heating energy consumption at cold outside temperatures. Instead, a window that allows less sunlight to pass through at a warm external temperature to cause less heating in the interior space would be required.

There is therefore a need for a device that can match the radiant energy flow to individual prevailing conditions. In particular, devices that automatically adapt to environmental conditions are needed.

The prior art additionally discloses means for reversible conversion from a light transmitting state to a less light transmitting state when a voltage is applied. The first state will hereinafter be referred to as the bright state, and the second state will be referred to as the dark state.

A possible embodiment of an electrically switchable device is an electrochromic device, which is especially presented in Seeboth et al, Solar Energy Materials & Solar Cells, 2000, 263-277. Further comments are provided by C. M. Lampert et al., Solar Energy Materials & Solar Cells, 2003, 489-499.

Other electrically switchable devices known from the prior art are based on the molecular alignment of the liquid crystal medium when an electric field is applied. Such devices are disclosed, inter alia, in US 4, 268, 126, US 4, 641, 922, US 5, 940, 150 and WO 2008/027031, and are also converted from a bright state to a dark transparent state under electrical control.

Although the above-described electrically switchable device is capable of setting the radiant energy flow, it has the disadvantage of requiring electrical control.

It would be desirable to provide a conversion element that automatically adapts to environmental conditions and that does not require manual control or is controlled by any other coupling device that can signal when a temperature deviation is detected.

In addition, it will be necessary to provide a conversion element that does not require any circuitry. The introduction of circuitry into the window is accompanied by additional work during the manufacture of the window and is necessarily accompanied by the risk of being sensitive to defects or short service life of the device. In addition, these devices require additional infrastructure, including power supplies.

Devices that are not electrically converted, such as temperature control (thermally reactive devices) are described inter alia in Nitz et al., Solar Energy 79, 2005, 573-582. A possible embodiment of such devices is a system based on separation between two phases above a certain temperature. Other embodiments are based on the temperature dependent nature of the hydrogel. However, such devices typically switch between a transparent state and a dark translucent (scattering) state, which is undesirable for applications that require the device to remain transparent in the dark state.

US 2009/0015902 and US 2009/0167971 disclose optical conversion elements comprising a liquid crystal medium between two polarizers. The liquid crystal medium has the property of rotating the plane of polarization of the light at a first temperature and not rotating or substantially rotating the plane of polarization of the light at a second temperature. Thus, a suitable configuration of the polarizer enables the device to allow more light to pass at the first temperature than at the second temperature. The two temperature-dependent states represent a bright state (first temperature) and a dark transparent state (second temperature), and are preferably changed from a nematic state (first temperature, liquid crystal medium rotating light polarization plane) to a liquid crystal medium. Caused by the same-sex state (the second temperature, the liquid crystal medium does not rotate the plane of polarization of the light).

The application US 2009/0015902 and US 2009/0167971 additionally disclose that liquid crystal media having low clearing points are suitable for use in such devices. The conversion process from the bright state to the dark transparent state caused by the phase transfer of the liquid crystal medium occurs only in the case of a typical solar radiation intensity heating device in the warm season. For this reason, a clear clear point below 85 ° C is revealed. The disclosed example is a liquid crystal medium comprising a liquid crystal mixture E7 and added 4'-hexyl-4-cyanobiphenyl (6CB) and having a clear point of 35 °C. Further, it is generally disclosed in the above application that the liquid crystal mixture ZLI1132 (Merck KGaA) having a clearing point of 72 ° C can also be used as a main component for preparing a liquid crystal medium for a switchable device. However, specific illustrative embodiments are not disclosed in this regard.

In this regard, it should be noted that the mixture E7 disclosed in US 2009/0015902 and US 2009/0167971 by the addition of an alkyl cyanobiphenyl compound such as 4'-hexyl-4-cyanobiphenyl has a weakened liquid crystal. Disadvantages of low temperature stability of the medium.

However, good low temperature stability of liquid crystal media is highly desirable because in many applications, the conversion elements are exposed to low temperatures for extended periods of time.

There is a continuing need for liquid crystal media suitable for use in thermal convertible devices. In particular, a liquid crystal medium that is transferred from a nematic state to an isotropic state (clear point) at a temperature within the operating temperature range of the conversion element is required. There is also a need for liquid crystal media having a high content of mixed cycloaliphatic and aromatic bicyclic compounds because such bicyclic compounds can be prepared in a cost effective manner. There is also a need for a liquid crystal medium having good low temperature storage stability and preferably combining the above characteristics.

To this end, the present invention provides a conversion element characterized in that it is thermally reactive and converts between a lower transmission state for radiant energy and a higher transmission state for radiant energy, the conversion element comprising a liquid crystal medium comprising One or more compounds of formula (I)

Wherein R ¹¹ and R ¹² are the same or different at each occurrence and are F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, an alkyl group having 1 to 10 C atoms , alkoxy or thioalkoxy, or alkenyl, alkenyloxy or thioalkenyloxy having 2 to 10 C atoms, or monocyclic, bicyclic or tricyclic ring having 3 to 10 C atoms An alkyl or cycloalkenyl group, wherein one or more of the above H atoms may be replaced by F, Cl, CN, and wherein one or more of the above CH ₂ groups may pass through O, S, - O-CO- or -CO-O-substituted; and wherein R ¹ is the same or different at each occurrence and is an alkyl or alkenyl group having from 1 to 10 C atoms, wherein one or more H atoms may pass through F Or Cl replacement;

Lined up

And

Lined up

And X is the same or different at each occurrence and is F, Cl, CN or an alkyl, alkoxy or thioalkoxy group having 1 to 10 C atoms, wherein one or more of the above groups The H atom may be replaced by F or Cl and wherein one or more CH ₂ groups may be replaced by O or S; and Z ¹¹ is selected from -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, - CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O- and a single bond are preferably selected from the group consisting of -CH ₂ O-, -OCH ₂ -, -CH ₂ CH ₂ - and a single bond.

Preferably, the liquid crystal medium additionally comprises one or more compounds of formula (II). In one embodiment of the invention, the compound of formula (II) is a compound of formula (II-1)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, an alkane having 1 to 10 C atoms. Alkyl, alkoxy or thioalkoxy and alkenyl, alkenyloxy or thioalkenyloxy having 2 to 10 C atoms, wherein one or more of the above H atoms may pass through F or Cl Substituting, wherein one or more CH ₂ groups of the above groups may be replaced by O, S, -O-CO- or -CO-O-; and R ^{1 is} as defined above;

Same or different and selected from

Wherein Z ²¹ is selected from the group consisting of -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O-, and a single bond, And Z ^{21 is} preferably a single bond. In an alternative embodiment of the invention, the compound of formula (II) is a compound of formula (II-2)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, an alkane having 1 to 10 C atoms. Alkyl, alkoxy or thioalkoxy and alkenyl, alkenyloxy or thioalkenyloxy having 2 to 10 C atoms, wherein one or more of the above H atoms may pass through F or Cl Substituting, wherein one or more CH ₂ groups of the above groups may be replaced by O, S, -O-CO- or -CO-O-; and R ^{1 is} as defined above;

Same or different and selected from

Wherein X is as defined above; and Z ²² is selected from the group consisting of -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O- and a single bond, and Z ^{22 is} preferably a single bond. In an alternative embodiment of the invention, the compound of formula (II) is a compound of formula (II-3)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, an alkane having 1 to 10 C atoms. Alkyl, alkoxy or thioalkoxy and alkenyl, alkenyloxy or thioalkenyloxy having 2 to 10 C atoms, wherein one or more of the above H atoms may pass through F or Cl Substituting, wherein one or more CH ₂ groups of the above groups may be replaced by O, S, -O-CO- or -CO-O-; and R ^{1 is} as defined above;

Same or different and selected from

Wherein Y is the same or different at each occurrence and is selected from H and X; X is as defined above; and Z ²³ is selected from the group consisting of -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O-, -CO-O-, -O-CO-, -CH=CH-, -CH=CX-, -CX=CH- and - CX=CX- and a single bond; and Z ^{23 is} preferably -CO-O- or a single bond; the limitation is

At least one of them is selected from

In an alternative embodiment of the invention, the compound of formula (II) is a compound of formula (II-4)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, an alkane having 1 to 10 C atoms. Alkyl, alkoxy or thioalkoxy and alkenyl, alkenyloxy or thioalkenyloxy having 2 to 10 C atoms, wherein one or more of the above H atoms may pass through F or Cl Substituting, wherein one or more CH ₂ groups of the above groups may be replaced by O, S, -O-CO- or -CO-O-; and R ^{1 is} as defined above;

Same or different and selected from

and Wherein X is as defined above; and Z ²⁴ is selected from the group consisting of -CO-O-, -O-CO-, -CH=CH-, -CH=CX-, -CX=CH-, and -CX=CX-; And Z ^{24 is} preferably -CO-O-.

Preferably, the liquid crystal medium additionally comprises one or more compounds selected from the group consisting of compounds of formula (III) and compounds of formula (IV)

Wherein R ₃₁ , R ₃ ² , R ⁴¹ and R ⁴² have the meanings indicated above with respect to R ²¹ and R ²² ;

Same or different at each occurrence and selected from

Wherein X and Y are as defined above; and Z ³¹ and Z ³² are the same or different at each occurrence and are selected from the group consisting of -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, - CH ₂ CH ₂ -, -OCH ₂ -, -CH ₂ O- and a single bond; and Z ⁴¹ , Z ⁴² and Z ⁴³ are the same or different at each occurrence and are selected from -CO-O-, -O-CO - and single button. According to a preferred embodiment of the invention, the liquid-crystalline medium comprises one or more compounds of formula (I) as defined above and one or more compounds of formula (II) as defined above and one or more selected from the group consisting of A compound of the formula (III) and a compound of the formula (IV). According to a preferred embodiment of the invention, X is the same or different at each occurrence and is selected from the group consisting of F, Cl, CN and an alkyl or alkoxy group having from 1 to 8 C atoms. Particularly preferably, the X system is selected from the group consisting of F and Cl, and particularly preferably, X is F.

Further preferably, Y is the same or different at each occurrence and is selected from the group consisting of H, F and Cl. Particularly preferably, Y is H. Further, preferably, R ¹¹ , R ¹² , R ²¹ and R ²² are the same or different at each occurrence and are selected from the group consisting of F, Cl, CN, R ¹ -O-CO-, R ¹ -CO-O-, a linear alkyl or alkoxy group having 1 to 10 C atoms and an alkenyl or alkenyloxy group having 2 to 10 C atoms, wherein one or more of the above H atoms may be replaced by F or Cl And wherein one or more of the above CH ₂ groups may be replaced by -O-CO- or -CO-O-, and R ^{1 is} as defined above.

According to a particularly preferred embodiment of the invention, the compound of formula (I) is a compound having the formula (I-1) to (I-2):

among them And R ¹¹ and R ¹² are as defined above. For the compound of formula (I), additionally preferably,

Lined up

For the compound of formula (I), additionally preferably

Lined up

, where X is as defined above. Particularly preferably, All are selected from the above preferred embodiments. According to a particularly preferred embodiment of the present invention, the compound of the formula (I-1) is a compound having the following formula (I-1a) to (I-1e):

Wherein R ¹¹ , R ¹² and X are as defined above. According to a particularly preferred embodiment of the present invention, the compound of the formula (I-2) is a compound having the following formula (I-2a) to (I-2b):

Wherein R ¹¹ , R ¹² and X are as defined above. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-1a) is a compound having the following formula (I-1a-1) to (I-1a-3):

Wherein R ¹¹ and R ¹² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- And R ¹ is an alkyl group having 1 to 10 C atoms. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-1b) is a compound having the following formula (I-1b-1)

Wherein R ¹¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms or an alkenyl group having 2 to 10 C atoms, wherein one or more CH ₂ groups in the above group are -O-CO- or -CO-O- substitution. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-1c) is a compound having the following formula (I-1c-1)

Wherein R ¹¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O-, and R ¹ is an alkyl group having 1 to 10 C atoms. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-1d) is a compound having the following formula (I-1d-1)

Wherein R ¹¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms or an alkenyl group having 2 to 10 C atoms, wherein one or more CH ₂ groups in the above group are -O-CO- or -CO-O- substitution. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-1e) is a compound having the following formula (I-1e-1)

Wherein R ¹¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms or an alkenyl group having 2 to 10 C atoms, wherein one or more CH ₂ groups in the above group are -O-CO- or -CO-O- substitution. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-2a) is a compound having the following formula (I-2a-1) and (I-2a-2)

Wherein R ¹¹ and R ¹² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- And R ¹ is an alkyl group having 1 to 10 C atoms. According to a more specific preferred embodiment of the present invention, the compound of the formula (I-2b) is a compound having the following formula (I-2b-1) and (I-2b-2)

Wherein R ¹¹ and R ¹² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- And R ¹ is an alkyl group having 1 to 10 C atoms.

According to a preferred embodiment, in the compound of formula (II-1),

equal

According to another preferred embodiment, in the compound of formula (II-2),

equal

According to another preferred embodiment, in the compound of formula (II-3),

Same or different at each occurrence and selected from

Where Y is as defined above; the constraint is

At least one of them is selected from

According to another preferred embodiment, in the compound of formula (II-4),

Same or different at each occurrence and selected from

Where X is as defined above. According to another preferred embodiment, R ²¹ and R ²² are the same or different at each occurrence and are F, Cl, CN or an alkyl or alkoxy group having from 1 to 10 C atoms or having from 2 to 10 C An alkenyl group of an atom wherein one or more of the above H atoms may be replaced by F or C1. A particularly preferred embodiment of the compound of the formula (II-1) is a compound having the following formula (II-1a)

Wherein R ²¹ and R ²² are as defined above. A particularly preferred embodiment of the compound of formula (II-2) is a compound of the following formula (II-2a)

Wherein R ²¹ and R ²² are as defined above. Particularly preferred examples of the compound of the formula (II-4) are compounds having the following formula (II-4a) to (II-4g)

Wherein R ²¹ and R ²² and X are as defined above. A preferred embodiment of the compound of the formula (II-1a) is a compound having the following formula (II-1a-1) and (II-1a-2)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are an alkyl or alkenyl group having from 1 to 10 C atoms, wherein one or more CH ₂ groups may be via -O-CO- or -CO- O-substitution, and R ¹ is an alkyl group having 1 to 10 C atoms. A preferred embodiment of the compound of the formula (II-2a) is a compound having the following formula (II-2a-1) to (II-2a-3)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- And R ¹ is an alkyl group having 1 to 10 C atoms. A preferred embodiment of the compound of the formula (II-4a) is a compound having the following formula (II-4a-1) to (II-4a-4)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- And R ¹ is an alkyl group having 1 to 10 C atoms. A preferred embodiment of the compound of the formula (II-4b) is a compound having the following formula (II-4b-1) and (II-4b-2)

Wherein R ²¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O-, and R ²² is F or Cl. A preferred embodiment of the compound of the formula (II-4c) is a compound having the following formula (II-4c-1)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- . A preferred embodiment of the compound of the formula (II-4d) is a compound having the following formula (II-4d-1)

Wherein R ²¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms or an alkenyl group having 2 to 10 C atoms, wherein one or more CH ₂ groups of the above groups may be Replaced by -O-CO- or -CO-O-. Preferred examples of the compound of the formula (II-4e) are compounds having the following formulas (II-4e-1) and (II-4e-2)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- And R ¹ is an alkyl group having 1 to 10 C atoms.

A preferred embodiment of the compound of the formula (II-4f) is a compound having the following formula (II-4f-1)

Wherein R ²¹ is the same or different at each occurrence and is an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O-, and R ¹ is an alkyl group having 1 to 10 C atoms. A preferred embodiment of the compound of the formula (II-4g) is a compound having the following formula (II-4g-1)

Wherein R ²¹ and R ²² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms, wherein one or more CH ₂ groups may be replaced by -O-CO- or -CO-O- . According to another preferred embodiment, in the compound of formula (III),

Same or different at each occurrence and selected from

, where X is as defined above. According to another preferred embodiment, in the compound of formula (III), Z ³¹ and Z ³² are the same or different at each occurrence and are -CO-O-, -O-CO-, -CF ₂ O-, - CH ₂ -CH ₂ - or a single bond. According to another preferred embodiment, in the compound of formula (III), R ³¹ and R ³² are the same or different at each occurrence and are F, Cl, CN or an alkyl or alkoxy group having from 1 to 10 C atoms. Or an alkenyl group having 2 to 10 C atoms, wherein one or more of the above H atoms may be replaced by F or Cl. According to a particularly preferred embodiment, the compound of formula (III) is a compound having the following formula (III-1) to (III-3)

Wherein the groups R ³¹ and R ³² and As defined above, and Z ³¹ and Z ³² are the same or different at each occurrence and are -CO-O-, -O-CO-, -CF ₂ O- or -CH ₂ -CH ₂ -. According to a preferred embodiment, in the compound of formula (III-1), Same or different at each occurrence and selected from

, where X is as defined above. According to another preferred embodiment, in the compound of formula (III-2), Same or different at each occurrence and selected from

According to another preferred embodiment, in the compound of formula (III-3), Same or different at each occurrence and selected from

and , where X is as defined above. According to a preferred embodiment of the present invention, the compound of the formula (III-1) is a compound having the following formula (III-1a) to (III-1c)

Wherein R ³¹ and R ³² are as defined above and wherein Same or different at each occurrence and selected from

, where X is as defined above. According to a particularly preferred embodiment of the present invention, the compound of the formula (III-1a) is a compound having the following formula (III-1a-1) to (III-1a-4)

Wherein R ³¹ is an alkyl group having 1 to 10 C atoms or an alkenyl group having 2 to 10 C atoms, and R ³² is F, Cl or an alkyl group or alkoxy group having 1 to 10 C atoms or has An alkenyl group of 2 to 10 C atoms, wherein one or more of the above H atoms may be replaced by F or Cl. According to a particularly preferred embodiment of the present invention, the compound of the formula (III-1b) is a compound having the following formula (III-1b-1) to (III-1b-5)

Wherein R ³¹ is an alkyl group having 1 to 10 C atoms and R ³² is F, Cl, CN or an alkyl group or alkoxy group, wherein one or more H atoms may be substituted by F or Cl. According to a particularly preferred embodiment of the present invention, the compound of the formula (III-1c) is a compound having the following formula (III-1c-1) to (III-1c-3)

Wherein R ³¹ is an alkyl group having 1 to 10 C atoms and R ³² is F, Cl, CN or an alkyl group having 1 to 10 C atoms or an alkenyl group having 2 to 10 C atoms. According to another particularly preferred embodiment of the present invention, the compound of the formula (III-2) is a compound having the following formula (III-2a) to (III-2b)

Wherein R ³¹ and R ³² are an alkyl group having 1 to 10 C atoms. According to another particularly preferred embodiment of the present invention, the compound of the formula (III-3) is a compound having the following formula (III-3a) to (III-3d)

among them Same or different at each occurrence and selected from

and Wherein X is as defined above, and R ³¹ and R ³² are as defined above. According to a preferred embodiment of the present invention, the compound of the formula (III-3a) is a compound having the following formula (III-3a-1) to (III-3a-7)

Wherein R ³¹ is an alkyl group having 1 to 10 C atoms and R ³² is F, Cl, CN or an alkyl group or alkoxy group, wherein one or more H atoms may be substituted by F or Cl. According to a preferred embodiment of the present invention, the compound of the formula (III-3b) is a compound having the following formula (III-3b-1)

Wherein R ³¹ and R ³² are an alkyl group having 1 to 10 C atoms. According to a preferred embodiment of the present invention, the compound of the formula (III-3c) is a compound having the following formula (III-3c-1) and (III-3c-2)

Wherein R ³¹ is an alkyl group having 1 to 10 C atoms and R ³² is F, Cl or an alkyl group or an alkoxy group, wherein one or more H atoms may be substituted by F or Cl.

According to a preferred embodiment of the present invention, the compound of the formula (III-3d) is a compound having the following formula (III-3d-1)

Wherein R ³¹ is an alkyl group having 1 to 10 C atoms and R ³² is F, Cl or an alkyl group or an alkoxy group, wherein one or more H atoms may be substituted by F or Cl. According to another preferred embodiment, in the compound of formula (IV),

Same or different at each occurrence and selected from , where X is as defined above. According to another preferred embodiment, in the compound of formula (IV), Z ⁴¹ to Z ⁴³ are the same or different at each occurrence and are -CO-O- or a single bond. According to another preferred embodiment, in the compound of formula (IV), R ⁴¹ and R ⁴² are the same or different at each occurrence and are alkyl groups having from 1 to 10 C atoms. According to a preferred embodiment of the present invention, the compound of the formula (IV) is a compound having the following formulas (IV-1) and (IV-2)

Where R ⁴¹ and R ⁴² and As defined above. According to a particularly preferred embodiment of the invention, the compound of formula (IV-1) is a compound having the following formulae (IV-1a) to (IV-1b)

Wherein R ⁴¹ and R ⁴² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms. According to another particularly preferred embodiment of the present invention, the compound of the formula (IV-2) is a compound having the following formula (IV-2a)

Wherein R ⁴¹ and R ⁴² are the same or different at each occurrence and are an alkyl group having 1 to 10 C atoms. According to a preferred embodiment of the invention, the total concentration of the compound of formula (I) is from 5% to 95%. More preferably, the concentration of the compound of formula (I) is from 15% to 90%, most preferably from 20% to 90%. Further preferably, the total concentration of the compound of formula (II) is from 0% to 90%. More preferably, the concentration of the compound of formula (II) is from 0% to 80%, most preferably from 0% to 75%. Further preferably, the total concentration of the compounds of formula (I) and (II) is from 40% to 100%. More preferably, the concentration of the compounds of formula (I) and (II) is from 50% to 100%, most preferably from 55% to 100%. Further preferably, the total concentration of the compounds of formula (III) and (IV) is from 0% to 40%.

The invention further relates to a liquid-crystalline medium comprising one or more compounds of the formula (I) as defined above and at least one of the other formulae (II) and (III) as defined above, in a total concentration of from 5% to 95% Or a compound of (IV) such that the total concentration of the compounds of formula (I), (II), (III) and (IV) is from 40% to 100%. According to a preferred embodiment of the invention, the liquid-crystalline medium comprises at least 5 different compounds selected from the group consisting of compounds of formula (I) to (IV). According to a particularly preferred embodiment, the liquid-crystalline medium comprises at least 6 different compounds selected from the group consisting of compounds of formula (I) to (IV). According to an even more preferred embodiment, the liquid-crystalline medium comprises at least 7 different compounds selected from the group consisting of compounds of formula (I) to (IV). The medium of the present invention may optionally contain other liquid crystal compounds to adjust physical properties. These compounds are known to the expert. The concentration thereof in the medium of the present invention is preferably from 0% to 30%, more preferably from 0.1% to 20% and most preferably from 1% to 15%. The liquid crystal medium of the present invention may contain a general concentration of a palmitic dopant as other additives. Preferred palmitic dopants are listed in Table E below. The total concentration of these other components is in the range of from 0% to 10%, preferably from 0.1% to 6%, based on the total mixture. The concentration of each of the individual compounds used is preferably in the range of 0.1% to 3%. The concentration values and ranges of the liquid crystal component and the liquid crystal dielectric compound in this application do not take into account the concentrations of these and similar additives. The liquid crystal medium of the present invention may contain a stabilizer of a general concentration as another additive. Preferred stabilizers are listed in Table F below. The total concentration of the stabilizer is in the range of from 0% to 10%, preferably from 0.0001% to 1%, based on the total mixture. According to a preferred embodiment of the invention, the clearing point (phase transition temperature of the nematic phase to the isotropic phase, T(N, I)) is below 60 °C. According to a particularly preferred embodiment, T(N,I) is below 50 °C. According to an even more preferred embodiment, T(N,I) is below 40 °C.

Preferred liquid crystal medium (liquid crystal medium I) for use in the conversion element of the present invention comprises - a total concentration of from 5% to 95% of one or more compounds of formula (I), - a total concentration of from 1% to 55% or a plurality of compounds of the formula (II-2a), - a total concentration of from 0% to 80% or a plurality of compounds of the formulae (II-4a), (II-4b), (II-4e) and (II-4f), and - a total concentration of 0% to 30% or a plurality of compounds of the formulae (III-1a), (III-1b), (III-3d), (IV-1) and (IV-2), wherein the formula (I) and (II) The total concentration of the compound is from 40% to 100%.

A more preferred liquid crystal medium (preferably liquid crystal medium I) for use in the conversion element of the present invention comprises - one of a total concentration of from 5% to 95% or a plurality of formulas (I-1a-1) to (I-1a-3) , (I-1b-1), (I-1c-1), (I-1d-1), (I-1e-1), (I-2a-1) to (I-2a-2) and a compound of I-2b-1) to (I-2b-2), - a total concentration of 1% to 55% or a plurality of compounds of the formula (II-2a-2), - a total concentration of 0% to 80% Or a plurality of formulas (II-4a-1) to (II-4a-4), (II-4b-1), (II-4e-1), (II-4e-2) and (II-4f-1) a compound, and - a total concentration of from 0% to 30% or a plurality of formulas (III-1a-2) to (III-1a-4), (III-1b-2) to (III-1b-4), Compounds IV-1a), (IV-1b) and (IV-2a) wherein the total concentration of the compounds of formula (I) and (II) is from 40% to 100%. Preferred liquid crystal medium (liquid crystal medium II) for use in the conversion element of the present invention comprises - a total concentration of from 5% to 95% of one or more compounds of formula (I), - a total concentration of from 0% to 80% or a plurality of compounds of the formulae (II-4a) and (II-4b), - a total concentration of from 1% to 80% of one or more of the compounds of the formulae (II-4e) and (II-4f), and - a total concentration of 0% to 30% or more of the formulae (III-1a) to (III-1c), (III-2a), (III-2b), (III-3a) to (III-3d), (IV-1) and IV-2) A compound wherein the total concentration of the compounds of formula (I) and (II) is from 40% to 100%.

A more preferred liquid crystal medium (preferably liquid crystal medium II) for use in the conversion element of the present invention comprises - one of a total concentration of from 5% to 95% or a plurality of formulas (I-1a-1) to (I-1a-3) , (I-1b-1), (I-1c-1), (I-1d-1), (I-1e-1), (I-2a-1) to (I-2a-2) and Compounds I-2b-1) to (I-2b-2), - a total concentration of from 0% to 80% or a plurality of formulas (II-4a-1) to (II-4a-4) and (II-4b) -1) a compound, - a total concentration of from 1% to 80% or a plurality of compounds of the formulae (II-4e-1), (II-4e-2) and (II-4f-1), and - a total concentration of 0 One to three or more of the formulas (III-1a-1) to (III-1a-4), (III-1b-1) to (III-1b-5), (III-1c-1) to ( III-1c-3), (III-2a), (III-2b), (III-3a-1) to (III-3a-7), (III-3b-1), (III-3c-1) To compounds of (III-3c-2), (III-3d-1), (IV-1a), (IV-1b) and (IV-2a), wherein the total concentration of the compounds of formula (I) and (II) is 40% to 100%. Preferred liquid crystal medium (liquid crystal medium III) for use in the conversion element of the present invention comprises - a total concentration of from 5% to 95% of one or more compounds of formula (I), - a total concentration of from 1% to 80% or a plurality of compounds of the formula (II-1a), - a total concentration of from 0% to 30% or a plurality of formulas (III-1a) to (III-1c), (III-2a), (III-2b), (III- 3a) to (III-3d), (IV-1) and (IV-2), wherein the total concentration of the compounds of formula (I) and (II) is from 40% to 100%.

A more preferred liquid crystal medium (preferably liquid crystal medium III) for use in the conversion element of the present invention comprises - one of a total concentration of from 5% to 95% or a plurality of formulas (I-1a-1) to (I-1a-3) , (I-1b-1), (I-1c-1), (I-1d-1), (I-1e-1), (I-2a-1) to (I-2a-2) and Compounds I-2b-1) to (I-2b-2), - a total concentration of 1% to 80% or a plurality of compounds of the formulae (II-1a-1) and (II-1a-2), - total concentration It is one of 0% to 30% or a plurality of formulas (III-1a-1) to (III-1a-4), (III-1b-1) to (III-1b-5), (III-1c-1) To (III-1c-3), (III-2a), (III-2b), (III-3a-1) to (III-3a-7), (III-3b-1), (III-3c- 1) to (III-3c-2), (III-3d-1), (IV-1a), (IV-1b) and (IV-2a), wherein the total of the compounds of formula (I) and (II) The concentration is 40% to 100%. Preferred liquid crystal media (liquid crystal media IV) for use in the conversion element of the present invention comprise - a total concentration of from 5% to 95% of one or more compounds of formula (I), - a total concentration of from 1% to 80% or a plurality of compounds of the formulae (III-1a), (III-1b) and (III-3d), - a total concentration of from 0% to 30% or a plurality of formulas (III-1a) to (III-1c), (III- Compounds 2a), (III-2b), (III-3a) to (III-3d), (IV-1) and (IV-2), wherein formula (I), (III-1a), (III-1b And the total concentration of the compound of (III-3d) is from 40% to 100%.

A more preferred liquid crystal medium (preferably liquid crystal medium IV) for use in the conversion element of the present invention comprises - a total concentration of from 5% to 95% or a plurality of formulas (I-1a-1) to (I-1a-3) , (I-1b-1), (I-1c-1), (I-1d-1), (I-1e-1), (I-2a-1) to (I-2a-2) and Compounds I-2b-1) to (I-2b-2), - a total concentration of 1% to 80% or a plurality of formulas (III-1a-2) to (III-1a-4), (III-1b -2) to (III-1b-4) and (III-3d-1) compounds, - the total concentration is from 0% to 30% or a plurality of formulas (III-1a-1) to (III-1a-4) , (III-1b-1) to (III-1b-5), (III-1c-1) to (III-1c-3), (III-2a), (III-2b), (III-3a- 1) to (III-3a-7), (III-3b-1), (III-3c-1) to (III-3c-2), (III-3d-1), (IV-1a), ( Compounds IV-1b) and (IV-2a), wherein (I), (III-1a-2) to (III-1a-4), (III-1b-2) to (III-1b-4) The total concentration of the compound (III-3d-1) is from 40% to 100%. A preferred liquid crystal medium (liquid crystal medium V) for use in the conversion element of the present invention comprises - a total concentration of from 5% to 95% of one or more compounds of the formula (I), - a total concentration of from 1% to 80% or a plurality of compounds of the formula (III-1b), (IV-1) and (IV-2), - a total concentration of from 0% to 30% or a plurality of formulas (III-1a) to (III-1c), (III- Compounds 2a), (III-2b), (III-3a) to (III-3d), (IV-1) and (IV-2), wherein formula (I), (III-1b), (IV-1 The total concentration of the compound of (IV-2) and (IV-2) is from 40% to 100%.

A more preferred liquid crystal medium (preferably liquid crystal medium V) for use in the conversion element of the present invention comprises - one of a total concentration of from 5% to 95% or a plurality of formulas (I-1a-1) to (I-1a-3) , (I-1b-1), (I-1c-1), (I-1d-1), (I-1e-1), (I-2a-1) to (I-2a-2) and Compounds I-2b-1) to (I-2b-2), - a total concentration of 1% to 80% or a plurality of formulas (III-1b-1), (III-1b-5), (IV-1a , (IV-1b) and (IV-2a) compounds, - a total concentration of 0% to 30% or a plurality of formulas (III-1a-1) to (III-1a-4), (III-1b- 1) to (III-1b-5), (III-1c-1) to (III-1c-3), (III-2a), (III-2b), (III-3a-1) to (III- 3a-7), (III-3b-1), (III-3c-1) to (III-3c-2), (III-3d-1), (IV-1a), (IV-1b) and IV-2a) a compound wherein the total concentration of the compounds of formula (I), (III-1b-1), (III-1b-5), (IV-1a), (IV-1b) and (IV-2a) is 40% to 100%. Preferred liquid crystal media (liquid crystal media VI) for use in the conversion element of the present invention comprise - one or more of a total concentration of from 5% to 95% of a compound of formula (I), - a total concentration of from 1% to 80% or a plurality of compounds of the formula (III-3a), (IV-1) and (IV-2), - a total concentration of from 0% to 30% or a plurality of formulas (III-1a) to (III-1c), (III- Compounds 2a), (III-2b), (III-3a) to (III-3d), (IV-1) and (IV-2), wherein formula (I), (III-3a), (IV-1 The total concentration of the compound of (IV-2) and (IV-2) is from 40% to 100%.

A more preferred liquid crystal medium (preferably liquid crystal medium VI) for use in the conversion element of the present invention comprises - one or more of a total concentration of from 5% to 95% or a plurality of formulas (I-1a-1) to (I-1a-3) , (I-1b-1), (I-1c-1), (I-1d-1), (I-1e-1), (I-2a-1) to (I-2a-2) and Compounds I-2b-1) to (I-2b-2), - a total concentration of 1% to 80% or a plurality of formulas (III-3a-5), (IV-1a), (IV-1b) and (IV-2a) compound, - a total concentration of from 0% to 30% or a plurality of formulas (III-1a-1) to (III-1a-4), (III-1b-1) to (III-1b- 5), (III-1c-1) to (III-1c-3), (III-2a), (III-2b), (III-3a-1) to (III-3a-7), (III- 3b-1), (III-3c-1) to (III-3c-2), (III-3d-1), (IV-1a), (IV-1b) and (IV-2a) compounds, wherein The total concentration of the compounds (I), (III-3a-5), (IV-1a), (IV-1b) and (IV-2a) is from 40% to 100%. The liquid crystal medium of the present invention is composed of several compounds, preferably 5 to 30, more preferably 6 to 20, and most preferably 6 to 16 compounds. These compounds are mixed according to methods known in the art. Usually, the amount of the compound to be used in a smaller amount is dissolved in the compound used in a larger amount. In the case where the temperature is higher than the clear point of the compound used at a higher concentration, the completion of the dissolution process is particularly easily observed. However, the medium can also be prepared by other conventional means, for example using a so-called premix (which may be, for example, a homologous or eutectic mixture of compounds) or using a so-called multi-bottle system (the components of which are ready to use the mixture itself).

The invention further relates to a process for the preparation of a liquid-crystalline medium as defined above, characterized by one or more compounds of the formula (I) and one or more compounds of the formula (II), (III) and/or (IV) and optionally Or a mixture of a plurality of other liquid crystal priming compounds and/or additives. According to a preferred embodiment of the invention, the conversion element comprises - a liquid crystal medium in the form of a thin layer, and - at least two polarizers preferably in the form of a thin layer, one of which is disposed on one side of the liquid crystal medium and the other is disposed On the other side of the liquid crystal medium.

The polarizer can be a linear or circular polarizer, preferably a linear polarizer. For linear polarizers, the polarization directions of the two polarizers are preferably rotated by a defined angle relative to each other.

Other layers and/or elements may be present, such as one or more respective alignment layers, one or more glass sheets, one or more band stop filters, and/or blocking light of a particular wavelength (eg, UV light) Color filter. Additionally, one or more insulating layers may be present, such as a low emissivity film. Additionally, one or more adhesive layers, one or more protective layers, one or more passivation layers, and one or more barrier layers may be present. A metal oxide layer may optionally be present, wherein the metal oxide may comprise two or more different metals and wherein the metal oxide may be doped with a halide ion, preferably fluorine. Preferably, the metal oxide layer comprises one or more of the following: indium tin oxide (ITO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), SnO ₂ and SnO ₂ :F (SnO doped with fluorine) ₂ ). Particularly preferred is a metal oxide layer comprising ITO.

In the liquid crystal medium layer, a spacer may be present. Exemplary embodiments of the above-described elements and their functions are known to those skilled in the art. For the purposes of this application, the term "polarizer" refers to a device or substance that blocks light in one polarization direction and transmits light in another polarization direction. Similarly, the term "polarizer" refers to a device or substance that blocks one type of circularly polarized light (right-handed or left-handed) and transmits another type of circularly polarized light (left-handed or right-handed). Blocking can occur by reflection and/or absorption. The reflective polarizer thus reflects one polarization direction or a type of circularly polarized light and transmits the opposite polarization direction or another type of circularly polarized light; and the absorption type polarizer absorbs one polarization direction or a type of circularly polarized light and transmits the opposite polarization direction or another A type of circularly polarized light. Reflection or absorption is usually not quantified, resulting in incomplete polarization of the light from the polarizer.

According to the invention, an absorbing and reflecting type polarizer can be used in the conversion element. Preferably, the polarizer of the present invention represents an optical film. Examples of reflective polarizers that can be used in accordance with the present invention are DRPF (diffuse reflective polarizer film, manufactured by 3M), DBEF (double-sided brightness enhancing film, manufactured by 3M), multilayers as described in US 7,038,745 and US 6,099,758. Polymer distribution Bragg reflector (DBR) and APF (advanced polarizer film, manufactured by 3M). In addition, a wire grid polarizer (WGP) that reflects infrared light as described in US 4,512,638 can be used. Wire grid polarizers that are partially reflected in the visible and ultraviolet light of the spectrum are described, for example, in US 6,122,103 and can also be used in accordance with the present invention. An example of an absorbing polarizer that can be used in accordance with the present invention is the Itos XP38 polarizing film or the Nitto Denko GU-1220 DUN polarizing film. Examples of circular polarizers that can be used in accordance with the present invention are APNCP37-035-STD (left-handed) and APNCP37-035-RH (dextrorotatory) from American Polarizers Inc. According to the invention, the conversion element is thermally reactive, indicating that its switching state is determined by temperature. In a preferred embodiment of the invention, no wires, circuits and/or switching networks are present in the conversion elements.

There is a conversion of the conversion element between a bright or open state of a conversion element that transmits a higher proportion of radiant energy and a dark or closed state of a conversion element that transmits a lower proportion of radiant energy.

The radiant energy is as defined above and is understood to encompass electromagnetic radiation in the UV-A zone, the VIS zone and the near infrared zone. Of course, the conversion element is not equally effective in the complete spectrum of radiant energy as defined above. Preferably, the off-state switching element blocks a high proportion of NIR and VIS light, particularly preferably a high proportion of NIR light.

A conversion element that converts only in one of the range VIS or NIR and converts in one range and permanently blocks another range (eg, converting VIS and permanently blocking NIR) is also preferred. According to a preferred embodiment of the invention, the conversion is achieved by varying the physical conditions of the liquid crystal medium. This change in the physical conditions of the liquid crystal medium is temperature dependent. It is preferably phase transfer. According to a particularly preferred embodiment of the invention, the conversion is effected by phase transfer of the liquid crystal medium from the liquid crystal phase to the isotropic phase occurring at a particular temperature. Even more preferably, the conversion is achieved by phase transfer of the liquid crystal medium from the nematic phase to the isotropic phase. Generally, the liquid crystal medium is in an isotropic state at a temperature higher than the phase transition temperature and in the liquid crystal, and is preferably in a nematic state at a temperature lower than the phase transition temperature.

Since the conversion of the device is caused by a temperature dependent change in the physical conditions of the liquid crystal medium, the liquid crystal medium represents an optically reactive thermal reactive element. However, other thermally reactive elements may be present. In order to use the conversion to regulate the radiant energy flow between the interior space and the environment (preferably between the building room and the exterior), a conversion operation is required at a typical temperature outside the building. Preferably, the conversion temperature of the conversion element is -20 ° C to 80 ° C, more preferably 10 ° C to 60 ° C and most preferably 20 ° C to 50 ° C. The switching temperature is defined as the temperature of the conversion element. Typically, this temperature is similar to the outside air temperature. However, under some conditions, such as direct exposure to sunlight, it may be significantly different from the outside air temperature. Also, in the case of a particular device setup, such as when the conversion element is located inside the insulated glass unit, the temperature of the conversion element can be significantly different from the outside air temperature. According to a preferred embodiment of the invention, the conversion of the conversion elements is effected by varying the physical conditions of the liquid crystal medium as described above. More preferably, this change in physical conditions represents a phase shift that occurs at a particular phase transition temperature. Preferably, the phase transition temperature is from -20 ° C to 80 ° C, more preferably from 10 ° C to 60 ° C and most preferably from 20 ° C to 50 ° C.

In an excellent embodiment of the invention, if the liquid crystal medium is in a liquid crystal state, the plane of polarization of the polarized light is rotated by a specific value by the liquid crystal medium. Conversely, if the liquid crystal medium is in an isotropic state, the plane of polarization of the polarized light is not rotated by the liquid crystal medium. Another aspect of the preferred embodiment is that the polarization directions of the polarizers are different from each other but are rotated at a defined angle relative to each other. In the preferred embodiment, the two states of the device are characterized as follows: In the bright state or the on state, the incident light is linearly polarized by the first polarizer. The linearly polarized light then passes through a liquid crystal medium in a liquid crystal state, which causes its polarization direction to rotate to define an angle.

After passing through the liquid crystal medium, the linearly polarized light is then directed to the second polarizer. A defined portion of the light that strikes the polarizer is transmitted through the polarizer. Preferably, there is an identity or only a relatively small deviation, preferably the value of the polarization planes of the two polarizers being rotated relative to each other and the value of the polarization plane of the polarized light being rotated by the liquid crystal medium of the nematic state. Here, the value of the plane of polarization of the polarized light rotated by the liquid crystal medium is understood to be the angle formed between the plane of polarization before entering the medium and the plane after leaving the medium from the plane of polarization. This angle can be generally from 0° to 180°. Accordingly, the flip of the angle X greater than 180° is equal to the flip of X minus n×180°, and the integer n is chosen such that the resulting angle X′ is at 0°. X'>180° range. However, it should be noted that the liquid crystal medium can be used to twist the plane of polarization of the polarized light passing therethrough with an absolute value greater than 180°. Even more than one complete flip (360°) can occur according to the invention, for example 2 Flip or 3 Flip the rotation. However, as explained above, the net value of the plane of polarization of the polarized light from the entry into the liquid crystal medium to the exit of the liquid crystal medium is in any case still between 0 and 180. Obviously, depending on the reference system used, the angle of rotation of the plane of polarization can also be expressed as a range of -90° to 90°, a negative value means a right turn, and a positive value means a left turn. In the bright state, most of the light passing through the first polarizer passes through the small deviation between the value of the polarization planes of the two polarizers relative to each other and the value of the polarization plane of the polarized light rotated by the liquid crystal medium. Second polarizer.

In order to cause the above-described bright state, the liquid crystal medium is required to have its liquid crystal state. Usually, this is the case of a temperature lower than the phase transition temperature. Thus, according to this preferred embodiment, the conversion element is in a bright state when it is at a temperature below the switching temperature. In order to make the dark transparent state or the closed state appear, the liquid crystal medium is required to be in an isotropic state. In this case, the incident light is again linearly polarized by the first polarizer. The polarized light then passes through a liquid crystal medium in an isotropic state. The liquid crystal medium in an isotropic state does not rotate the polarization direction of the linearly polarized light. After passing through the liquid crystal medium, the polarization direction of the linearly polarized light is maintained to the second polarizer. As described above, the polarization direction of the second polarizer is rotated with respect to the polarization direction of the first polarizer, in which case, as explained above, this is also the polarization direction of the linearly polarized light that strikes the second polarizer. Since the polarization direction of the polarized light is inconsistent with the polarizer, but is related to the rotation limit value of each other, the value is the same as the value of the two polarizers rotating relative to each other, and now only a part of the light is transmitted. The amount of light transmitted in this state is smaller than the amount of light transmitted in the bright state.

As described above, in the dark state or the closed state, the liquid crystal medium is in its isotropic state. Usually, this is the case where the temperature is higher than the phase transition temperature. Therefore, according to this preferred embodiment, when the conversion element is at a temperature higher than the switching temperature, it is in a dark state or a closed state. Depending on the desired transmittance of the conversion element in the dark transparent state, the polarization directions of the two polarizers can be rotated by any arbitrary value with respect to each other. The preferred value is in the range of 45 to 135, more preferably 70 to 110, and most preferably 80 to 100. The value of the plane of polarization of the polarized light of the liquid crystal medium in the nematic state does not have to be the same as the value of the polarization directions of the two polarizers with respect to each other. Preferably, the values are similar, and the preferred deviation is excellently less than 30° and optimally less than 20°. The value of the plane of polarization of the polarized light of the liquid crystal medium in the nematic state is preferably in the range of 0 to 360. However, values greater than 360 may also be present in accordance with the present invention.

In order to adjust the internal temperature of the building, the settings described above are generally preferred. At low temperatures, the radiant energy is allowed to flow because the switching element is in an open state. This leads to an increase in the heat intake of the building and a reduction in heating costs. At high temperatures, the conversion element is off and restricts radiant energy from flowing into the building. This reduces undesired heat intake at high temperatures and reduces air conditioning costs. Depending on the angle at which the two polarizers are offset from each other, and depending on whether the polarizer polarizes all incident light or only a portion of it, the light is transmitted more or less through the switching element in the off state. The full polarizer is in the "cross" position (the polarization direction is rotated by 90° for each other), and the light is not transmitted when it is off. If the polarization direction of the polarizer is not rotated by 90°, some light can be transmitted even in the off state. This configuration is in accordance with the needs of the present invention. Similarly, among other factors, the amount of light transmitted by the switching element in the on state depends on the polarizer efficiency and the angle of the polarization direction of the liquid crystal medium rotating linearly polarized light and the angle of polarization of the two polarizers relative to each other. Depending on the difference. In the case where the full polarizer and the angle of rotation are completely coincident, up to 50% of the light is transmitted through the means in the on state, and ideally, 0% of the transmitted light in the off state.

Filtering out the 50% light system filters (absorbs or reflects) 50% of the unpolarized incident light due to a fully linear polarizer. If a non-complete polarizer is used, the transmittance of the light-passing device can therefore be significantly increased, which may be desirable. It should be mentioned herein that numerous other combinations of polarizer orientation and polarization direction rotation caused by liquid crystal media can be used in the present invention. Other embodiments of the invention include a liquid crystal medium that scatters light in a first temperature range and is transparent in a second temperature range, and the second temperature range can be higher or lower than the first temperature range. According to another embodiment of the invention, the liquid crystal medium can affect the polarization state of the circularly polarized light.

In accordance with another embodiment of the present invention, a liquid crystal medium exhibits a guest-host system that, in addition to one or more liquid crystal compounds, also contains dye molecules or other materials that exhibit absorption or reflection characteristics. According to this embodiment, the liquid crystal medium provides orientation for the dye molecules in the liquid crystal state (low temperature), but does not provide the orientation in the isotropic state (high temperature). The guest-host system exhibits temperature-dependent transmission characteristics because the dye molecules interact in different ways depending on the degree of orientation of the light. In accordance with the present invention, when the liquid crystal medium exhibits a guest-host system, it is preferred that only one polarizer or no polarizer be used at all in the apparatus of the present invention. Further, according to the present invention, when the liquid crystal medium exhibits a guest-host system, it is preferred to use a twisted nematic orientation of the liquid crystal medium or a vertical alignment orientation of the liquid crystal medium.

According to a preferred embodiment of the present invention, the rotation of the polarized light by the liquid crystal medium in a liquid crystal state is caused by the molecular alignment of the liquid crystal medium. According to the invention, this alignment is typically achieved by an alignment layer in direct contact with the liquid crystal medium. Preferably, the alignment layer appears as two outer boundaries of the liquid crystal dielectric layer. For example, two alignment layers facing each other can be attached to the interior of the compartment that encloses the liquid crystal medium. According to another preferred embodiment, the alignment layer constitutes a compartment enclosing the liquid crystal medium. The alignment layer can be prepared by rubbing a polymer or polymer film with a rubbing cloth, sandpaper, or some other suitable material. Polyimine films are particularly suitable for use herein, but orientation can also be achieved on other types of polymers.

According to another preferred embodiment, the alignment layer and the polarizer layer are not separated but form a single layer. It can for example be glued or laminated together. The polarizer can be induced to induce alignment characteristics of the liquid crystal molecules, for example, by rubbing, scratching, and/or micropatterning the polarizer layer. For a detailed description, reference is made to the patent application US 2010/0045924, the disclosure of which is incorporated herein by reference. A preferred embodiment of the conversion element of the present invention comprises a liquid crystal medium in a container of transparent material, preferably a transparent polymer or glass. Furthermore, the conversion element comprises two or more alignment layers which are in direct contact with the liquid crystal medium. For example, an alignment layer can be attached to the inner surface of the container described above. According to another preferred embodiment, the inner surface of the container can be used as the alignment layer itself. Furthermore, as described above, the conversion element comprises two or more polarizers which may be present in the form of a polarizing foil. Other rigid or flexible layers may be present, such as other glass sheets, band stop filters (such as UV blocking films), and/or insulating layers (such as low emissivity films). According to this embodiment of the invention, the conversion element is rigid due to the presence of a layer of rigid material and cannot be bent or rolled up for storage and/or transportation.

According to another preferred embodiment of the invention, the liquid crystal medium is enclosed by a flexible polymer sheet. The flexible polymer sheet can be presented as a polarizer and/or an alignment layer. Other layers such as those described above may additionally be present. For a detailed description, reference is made to the patent application US 2010/0045924, the disclosure of which is incorporated herein by reference. According to this embodiment, the conversion element is flexible and bendable and/or rolled up.

According to another preferred embodiment of the invention, the liquid crystal medium has a solid or gel-like consistency. According to this embodiment, a rigid container for a liquid crystal medium is not required, and the need for a glass and/or rigid polymer sheet present in the conversion element is eliminated. An advantage of this embodiment of the invention is that the conversion element is less susceptible to damage and can be fabricated in the form of a rollable flexible sheet. The conversion element can then be cut from this roll into any shape or size which simplifies the storage, transport and manufacture of the device.

In order to obtain the above solid or gel-like consistency liquid-crystalline medium, the following procedure can be used in accordance with the present invention. The liquid crystal medium can be embedded in the optically transparent medium, for example, in the form of individual compartments, such as liquid crystal media droplets. The optically transparent medium is preferably a polymeric material, particularly preferably an isotropic thermoplastic, duroplastic or elastomeric polymer. The polymeric material is especially preferably a thermoplastic or elastomeric polymer. Examples thereof are NCAP films (NCAP = nematic curvilinear aligned phases) and PDLC films (PDLC = polymer dispersed liquid crystals). The NCAP film can be obtained by a method of sufficiently mixing a polymeric material (e.g., polyvinyl alcohol), a liquid crystal medium, and a carrier material (such as water) in a rubber mill. The carrier material is then removed, for example by evaporation. A detailed procedure for forming a NCAP membrane is described in US 4,435,047.

The PDLC film described in, for example, US 4,688,900; WO 89/06264; EP 0272585 and Mol. Cryst. Liq. Cryst. Nonlin. Optic, 157, (1988), 427-441 can be uniformly mixed with a liquid crystal medium and a monomer / or oligomers (which will then react with the polymer matrix) are obtained. After polymerization, phase separation is induced in which compartments or droplets in the form of a liquid crystal medium are dispersed in a polymer matrix.

According to another embodiment of the invention, the liquid crystal medium is in the form of a continuous phase in a polymer network (PN system). Such systems are described in detail in, for example, EP 452 460, EP 313 053 and EP 359 146. The polymer network generally has a sponge-like structure in which the liquid crystal medium can float freely. According to a preferred embodiment, it is formed by polymerization of a monoacrylate or polyacrylate monomer.

Preferably, the liquid crystal medium is present in the PN system in a percentage of more than 60%, particularly preferably 70-95%. The polymer network system can be prepared by inducing polymerization in a mixture of individual monomers and/or oligomers comprising a liquid crystal medium and forming a three-dimensional polymer network. According to a preferred embodiment, the polymerization is initiated by photoinitiation. According to another embodiment of the invention, the polymer does not form a network, but is dispersed in the form of small particles in a liquid crystal medium which is present in the PN network system as a continuous phase. The liquid crystal medium of the present invention is particularly suitable for use in the above-described PDLC system, NCAP system, and PN system.

A further object of the invention is therefore a composite system comprising a liquid crystal medium and a polymer as defined above, preferably a microporous polymer. According to the invention, the conversion element can be attached to any kind of transparent window, building facade, door or roof, including private, public and commercial buildings; in containers for transportation, storage and habitat; and in any vehicle They are the same. It is especially preferred to attach to an insulated glass unit (IGU) or multi-pane window and/or as an integrated element for an insulated glass unit or a multi-pane window. According to a preferred embodiment of the invention, the conversion element is attached to the outside of the window, the facade of the building, the door or the roof. According to another preferred embodiment, the conversion element is placed inside the IGU, wherein the conversion element can be protected from adverse effects such as extreme weather conditions and degradation by UV exposure. In an alternative embodiment, the conversion element is attached to the inner side of the window, the facade of the building, the door or the roof.

According to an embodiment of the invention, the conversion element covers the entire surface of the window. In this case, the switching device maximizes the control of the radiant energy flow. According to another embodiment of the invention, the conversion element covers only a portion of the window surface such that a gap that is not covered by the conversion element is left. These gaps may be in the form of strips, dots, and/or larger regions. This allows parts of the window to switch between bright and dark states, while other parts are always bright. This leads to an increase in the transparency of the window, especially when it is off. The conversion element can be used according to the invention to regulate the flow of radiant energy between the interior space and the environment. Particularly preferably, it is used to adjust the energy flow in the form of VIS light and NIR light or only VIS light, or to adjust the combination of VIS light and permanently blocked NIR light. Further preferably, the conversion element automatically adjusts the radiant energy flow by its ability to switch between temperature-dependent transitions between the on state and the off state without manual control. According to a particularly preferred embodiment of the invention, a conversion element is used to regulate the internal temperature of the building and/or the vehicle. For the purposes of the present invention, all concentrations are expressed in mass percent unless otherwise specifically indicated and refer to the respective mixture or mixture components unless otherwise specifically indicated.

The clear point of the liquid crystal mixture was determined in a capillary. The suitable instrument is the Mettler Toledo FP90. Typically, the liquid crystal mixture shows a clear range. By definition, the clear point is the lowest temperature at which all materials are still in the nematic range.

Alternatively, the clear point of the mixture in the display can be determined in a normally white mode TN chamber in a microscope hot stage. The transition from the nematic state to the isotropic state results in black spots in the TN chamber. When heated, the temperature at which the first occurrence of these points is measured is a clear point. For the application of the invention, it relates to the long term storage characteristics of the liquid crystal medium in the display. To determine the long-term storage characteristics in the display, the liquid crystal mixture was filled into several TN chambers having a thickness of 5 to 6 μm. The TN chamber receives the end seals, obtains a polarizer attachment in a normally white mode setting and stores in the refrigerator for up to 1000 hours at a given temperature. The dark spots in the TN chamber indicating crystallization or smectic-nematic transfer were visually observed at defined time intervals. If the TN chamber does not show dark spots at the end of the test period, pass the test. Otherwise, the time it takes to detect the first dark spot is recorded as a measure of long-term storage stability. In the present application and especially in the following examples, the structure of the liquid crystal compound is represented by an abbreviation, which is also referred to as an "acronym". Tables A to C show the structural elements of the compounds and their corresponding abbreviations. All groups C _n H _2n+1 , C _m H _2m+1 , C _p H _2p+1 and C _q H _{2q+1 are} preferably linear alkyl groups having n, m, p and q C atoms, respectively. . All groups C _n H _2n , C _m H _2m , C _p H _2p and C _k H _{2q are} preferably (CH ₂ ) _n , (CH ₂ ) _m , (CH ₂ ) _p and (CH ₂ ) _{q , respectively} ; And -CH=CH- is preferably a trans- E- extended vinyl group. The indices n, m, p and q preferably have a value of 1 to 10.

Note: From the left to the right of the chemical structure, if only one index appears, the index used is n; if two indices appear, it is n and m; if three indices appear, it is n, m and p; When four indices appear, they are n, m, p, and q. This nomenclature can be extended if necessary. Therefore, the right alkyl-C _n H _2n+1 corresponding to -n according to the acronym nomenclature (see the table below) can also be determined as the group corresponding to -m -C _m H _2m depending on the selected index. ₊₁ , or a group corresponding to -p - _{p p} H _2p+1 , or a group corresponding to -q -C _q H _2q+1 . The same applies to all other groups of Table C, wherein the letter n is used to denote an alkyl group having n carbon atoms and 2n+1 hydrogen atoms or an alkylene group having n carbon atoms and 2n hydrogen atoms.

Table A lists the symbols used for the loop elements, Table B lists the symbols for the linking groups, and Table C lists the symbols for the left and right hand end groups of the molecule.

Wherein n and m are each an integer and three points "..." indicate that other symbols of the table may exist at the location. The structures in Tables D1 and D2 below are preferred compounds for use in the apparatus of the present invention. The structures listed in Table D1 are given along with the acronym names of the systems described above.

Table E lists the palmitic dopants which are preferred for use in the liquid crystal media of the present invention.

In a preferred embodiment of the invention, the medium of the invention comprises one or more compounds selected from the group of compounds of Table E.

Table E lists stabilizers which are preferably used in the liquid crystal medium of the present invention.

In a preferred embodiment of the invention, the medium of the invention comprises one or more compounds selected from the group of compounds of Table F.

Instance

The following exemplary liquid crystal mixtures are listed for purposes of illustrating the invention and are not to be construed as limiting in any way.

The composition of the liquid crystal mixture and its clearing point and its long-term storage characteristics are listed below. Those skilled in the art have learned from the information given below which characteristics can be obtained using the mixtures of the invention. It is also taught how to modify the composition of the mixture to achieve the desired characteristics, especially the defined temperature and high long-term stability of the clear point.

A liquid crystal mixture having the compositions listed in the following table was prepared, and its clear point and long-term storage characteristics were measured.

As described in the description of the invention of the present application, the clearing point of the liquid crystal medium of the present invention is preferably from -20 ° C to 80 ° C, more preferably from 10 ° C to 60 ° C and most preferably from 20 ° C to 50 ° C. Even more preferably, the clearing point is from 20 ° C to 40 ° C.

An exemplary mixture having a relatively high resolution point (> 70 ° C, especially > 80 ° C) is preferably used in combination with a mixture having a lower clearing point for use as a so-called two-bottle system.

1) Example of liquid crystal medium I

2) Example of liquid crystal medium II

3) Example of liquid crystal medium III

4) Example of liquid crystal medium IV

5) Example of liquid crystal medium V

6) Example of liquid crystal medium VI

7) Use of liquid crystal medium in conversion components

According to the procedure of US 2009/0015902, the mixtures 1 to 21 of the present invention are used as a liquid crystal medium in a conversion element.

In order to assemble the conversion element, the procedure described in paragraphs [0050]-[0055] of the above patent application is followed, but an exemplary mixture of the invention (Examples-1 to 21) is used instead of the one disclosed in the application. Mixture (5 parts of 6CB (4'-hexyl-4-cyanobiphenyl), 1.25 parts of mixture E7 and 0.008 parts of S-811).

Using the inventive mixtures (Examples 1 to 21), conversion elements having a high lifetime can be obtained. The switching temperature of the conversion element is close to the clear point of the mixture (10 ° C to 80 ° C, which is the preferred operating range of the component).

This display allows for high device stability and controlled clearing points using the inventive mixtures.

These findings support the idea of the present invention in liquid crystal mixtures for use in conversion elements.

Claims (16)

A conversion element characterized in that it is thermally reactive and converts between a lower transmission state for radiant energy and a higher transmission state for radiant energy, the conversion element comprising a liquid crystal medium comprising one or more (I) compound Wherein R ¹¹ and R ¹² are the same or different at each occurrence, and are F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, an alkyl group having 1 to 10 C atoms. , alkoxy or thioalkoxy, or alkenyl, alkenyloxy or thioalkenyloxy having 2 to 10 C atoms, or monocyclic, bicyclic or tricyclic ring having 3 to 10 C atoms An alkyl or cycloalkenyl group, wherein one or more of the above H atoms may be replaced by F, Cl, CN, and wherein one or more of the above CH ₂ groups may pass through O, S, - O-CO- or -CO-O-substituted; and wherein R ¹ is the same or different, each occurrence, is an alkyl or alkenyl group having from 1 to 10 C atoms, wherein one or more H atoms may pass through F Or Cl replacement; Lined up And Lined up And X is the same or different at each occurrence of F, Cl, CN or an alkyl, alkoxy or thioalkoxy group having 1 to 10 C atoms, wherein one or more of the above groups The H atom may be replaced by F or Cl and wherein one or more CH ₂ groups may be replaced by O or S; and Z ¹¹ is selected from -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, - CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O-, and a single bond, wherein the conversion of the conversion element is achieved by phase transfer of the liquid crystal medium from an isotropic phase to a nematic phase. The conversion element of claim 1, wherein the liquid crystal medium further comprises one or more compounds of the formula (II), wherein in one embodiment of the invention, the compound of the formula (II) is a compound of the following formula (II-1) Wherein each of R ²¹ and R ²² is the same or differently selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, having 1 to 10 C atoms. An alkyl group, an alkoxy group or a thioalkoxy group and an alkenyl group, an alkenyloxy group or a thioalkenyloxy group having 2 to 10 C atoms, wherein one or more of the above H atoms may be F or Cl is substituted, and wherein one or more of the above CH ₂ groups may be replaced by O, S, -O-CO- or -CO-O-; and R ¹ is as defined in claim 1; and Are selected from the same or different , ,and Wherein Z ²¹ is selected from the group consisting of -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O-, and a single bond; And wherein, in an alternative embodiment of the invention, the compound of formula (II) is a compound of formula (II-2) Wherein each of R ²¹ and R ²² is the same or differently selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, having 1 to 10 C atoms. An alkyl group, an alkoxy group or a thioalkoxy group and an alkenyl group, an alkenyloxy group or a thioalkenyloxy group having 2 to 10 C atoms, wherein one or more of the above H atoms may be F or Cl is substituted, and wherein one or more of the above CH ₂ groups may be replaced by O, S, -O-CO- or -CO-O-; and R ¹ is as defined in claim 1; and Are selected from the same or different ,and Wherein X is as defined in claim 1; and Z ²² is selected from the group consisting of -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O- and a single bond; and wherein, in an alternative embodiment of the invention, the compound of formula (II) is a compound of the following formula (II-3) Wherein each of R ²¹ and R ²² is the same or differently selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, having 1 to 10 C atoms. An alkyl group, an alkoxy group or a thioalkoxy group and an alkenyl group, an alkenyloxy group or a thioalkenyloxy group having 2 to 10 C atoms, wherein one or more of the above H atoms may be F or Cl is substituted, and wherein one or more of the above CH ₂ groups may be replaced by O, S, -O-CO- or -CO-O-; and R ¹ is as defined in claim 1; and Are selected from the same or different , , ,and Wherein Y is the same or differently selected from H and X at each occurrence; X is as defined in claim 1; and Z ²³ is selected from -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -OCH ₂ -, -CH ₂ O-, -O-, -CO-O-, -O-CO-, -CH=CH-, -CH=CX-, - CX=CH- and -CX=CX- and single bond; the constraint is and At least one of them is selected from , ,and And wherein, in an alternative embodiment of the invention, the compound of formula (II) is a compound of formula (II-4) Wherein each of R ²¹ and R ²² is the same or differently selected from the group consisting of F, Cl, CN, NCS, R ¹ -O-CO-, R ¹ -CO-O-, having 1 to 10 C atoms. An alkyl group, an alkoxy group or a thioalkoxy group and an alkenyl group, an alkenyloxy group or a thioalkenyloxy group having 2 to 10 C atoms, wherein one or more of the above H atoms may be F or Cl is substituted, and wherein one or more of the above CH ₂ groups may be replaced by O, S, -O-CO- or -CO-O-; and R ¹ is as defined in claim 1; and Are selected from the same or different and Where X is as defined in claim 1; and Z ²⁴ is selected from -CO-O-, -O-CO-, -CH=CH-, -CH=CX-, -CX=CH-, and -CX =CX-. The conversion element of claim 1 or 2, wherein the liquid crystal medium further comprises one or more compounds selected from the group consisting of a compound of formula (III) and a compound of formula (IV) Wherein R ^31, R ^32, R ⁴¹ and R ⁴² having the meaning of request item 2 R ²¹ and R ²² shown in the; and to and to Selected at the same time or differently at each occurrence , , ,and Wherein X and Y are as defined in claim 2; and Z ³¹ and Z ³² are the same or differently selected from each of -CO-O-, -O-CO-, -CF ₂ O-, - at each occurrence. OCF ₂ -, -CH ₂ CH ₂ -, -OCH ₂ -, -CH ₂ O-, and a single bond; and Z ⁴¹ , Z ⁴² and Z ⁴³ are the same or differently selected from -CO-O at each occurrence -, -O-CO- and single bond. A conversion element according to claim 1 or 2, wherein the compound of the formula (I) is a compound of the following formula (I-1) to (I-2) among them Lined up , , and And Lined up , and And wherein X and R ¹¹ and R ¹² are as defined in claim 1. A conversion element according to claim 1 or 2, wherein the compound of the formula (II-1) is a compound of the following formula (II-1a) Wherein R ²¹ and R ²² are as defined in claim 2. The conversion element of claim 2, wherein the compound of the formula (II-2) is a compound of the following formula (II-2a) Wherein R ²¹ and R ²² are as defined in claim 2. The conversion element of claim 2, wherein the compound of the formula (II-4) is a compound of the following formula (II-4a) to (II-4g) Where X is as defined in claim 1 and R ²¹ and R ²² are as defined in claim 2. The conversion element of claim 3, wherein the compound of formula (III) is a compound of the following formula (III-1) to (III-3) Wherein the groups R ³¹ and R ³² and to Is as defined in claim 3; and Z ³¹ and Z ³² are the same or different at each occurrence -CO-O-, -O-CO-, -CF ₂ O- or -CH ₂ -CH ₂ -. The conversion element of claim 3, wherein the compound of the formula (IV) is a compound of the following formulas (IV-1) and (IV-2) Where R ⁴¹ and R ⁴² and to As defined in request 3. A conversion element according to claim 1 or 2, characterized in that the X system is selected from the group consisting of F and Cl. The conversion element of claim 1 or 2, wherein the total concentration of the compound of the formula (I) is from 15% to 90%. A conversion element as claimed in claim 1 or 2, wherein no wires, circuits and/or switching networks are present in the conversion element. A liquid crystal medium comprising one or more of a total concentration of 5% to 95% of a compound of the formula (I) according to claim 1 and at least one of the other formulae (II) and (III) of claim 2 and/or 3. Or (IV) a compound such that the total concentration of the compounds of the formulae (I), (II), (III) and (IV) is from 40% to 100%, wherein the palmitic dopant is not more than 6% The concentration is present in the medium. A use of the liquid crystal medium of claim 13 for use in a thermally reactive optical conversion element. A composite system comprising the liquid crystal medium of claim 13 and a polymer, preferably a microporous polymer. A use of a conversion element as claimed in one or more of claims 1 to 12 for regulating the flow of radiant energy between the interior space and the environment.